1. Field of the Invention
The invention is related to treatment of liquid radioactive wastes and, in particular, to a bio-safe polymer sorbent for selective binding of Sr and Cs isotopes from a liquid medium.
2. Description of the Related Art
Currently, there are several basic types of radionuclide sorbents in the form of a sorption matrix of inorganic salts—i.e., chelating agents such as tetraborates (RU Patent No. 2200994), acrylates (JP Patent No. 2005008753, 2005), acetates (RU Patent No. 2200994), silicates (RU Patent No. 2154317, RU Patent No. 2189650) and their zeolite modifications, strontium chelator based on the diaza-complex and silicic zeolite matrix developed by NIMS, Japan (National Institute for Materials Science) (http:**.nims.go.jp/eng/news/press/2011/07/p201107270.html), aluminum silicates, aluminum substituted alumen (RU Patent No. 2200994), orthophosphates (RU Patent No. 2200994).
The common drawback of the above mentioned compounds is the complexity of their synthesis, toxicity, and a relatively low sorptive capacity.
U.S. Pat. No. 4,995,985 describes a sorbent for the selective binding of Sr and Cs—propylene glycol alginate having, in the composition of a side chain, the polymer of gelatin, which is used as a ground for growing the bacterial culture, which is included in the sorbent. A disadvantage of the sorbent is that the distribution ratio of Sr and Cs between the phase with sorbent and the phase with deactivated water medium is 1371 and 103, respectively, and the coefficient value decreases sharply with the increase of the exposure time of the sorbent to the deactivated liquid medium, which indicates a weak binding of radio-nuclides. Another disadvantage is the lack of the specific capacity of the sorbent (i.e., a specific binding site—the larger the specific capacity, the better for the intended purpose).
Thus, the existing sorbents have insufficient sorption capacity. Moreover, they are not considered to be safe bio-compatible substances, which limits their use not only in medicine, but also in biotechnology, as well as during purification of waste waters and other polluted waters that can absorb the residues of sorbent, which is unsafe for biological environment.
Accordingly, it is desired to provide a sorbent with high and specific sorption capacity in compliance with the requirements of biocompatibility and safety with respect to the diverse biological objects. It is also desired to produce a raw mixture for sorbent production.